In the manufacture of matrix boards for use in forming flexographic printing plates, impressions are formed in the matrix boards using a master. The impression is usually achieved by pressing the matrix material against the master plate under high pressure and heat. The high temperature and pressure applied against matrix boards coated with prior art coatings causes distortion of the rubber or photopolymer coating whereby unsatisfactory matrices are obtained and/or the masters are damaged. This is because prior art coatings are organic solvent-based compositions and therefore they have a tendency to lock-in moisture which blisters during pre-heating.
In addition, applying the prior art coatings to the board within a desired thickness is difficult and time consuming. For example, a typical single pass coating using prior art compositions is limited in thickness to 0.020". As is apparent, several passes are then required if a thickness of 0.200" is desired.
Finally, prior art coating compositions for matrix boards employ so-called "one step" phenolic resins. One step phenolic resins are formed as a reaction product of formaldehyde and phenol in the presence of a catalyst. The reaction is terminated prior to complete crosslinking to permit final crosslinking during molding of the finished product. Coatings based upon such one step phenolic resins have been found to have a relatively short shelf life.